Syndrome X (insulin resistance, obesity, hypertension, lipid abnormalities, and cardiovascular disease) is well described and is associated with significant morbidity and mortality. Although it has been almost exclusively studied in adults, it probably exists in its early stages in childhood. Insulin resistance may be the first step in the development of this syndrome. As part of a hypertension study, we are presently studying blood pressure, insulin resistance, lipid profiles, and cardiovascular function in 350-400 normal school children, age 11-14 years. The purpose of the present proposal is to study the parents of insulin resistant and insulin sensitive children in order to explore familial relationships and genetic susceptibility to Syndrome X. Parents will be admitted to the CRC for an outpatient visit, consisting of an oral glucose tolerance test with measurement of glucose, insulin, and C-peptide; serum lipid measurements; echocardiography; and measurement of body fat by a stable isotope method. Analyses will be conducted between families in an attempt to establish significant relationships and determine differences between families with high and low insulin sensitivity.